The present invention relates generally to spectrophotometry, near-field microscopy, and scanning probe microscopy. Specifically, it relates to a scanning probe microscope assembly and corresponding method for making spectrophotometric and near-field measurements in addition to conventional scanning probe measurements.
In the past, near-field optical microscopes, such as those described in U.S. Pat. No. 4,604,520, have incorporated spectrophotometer in order to obtain information about the composition of the specimen being examined. However, they are plagued by the extremely slow rate at which the specimen area can be scanned. This problem has severely limited the use of near-field optical microscopes and spectrophotometer for commercially important applications in the biological and industrial fields. In addition, near-field optical microscopes can not achieve the resolution of scanning probe microscopes.
On the other hand conventional scanning probe microscopes, such as scanning tunneling microscopes and atomic force microscopes, have been able to make only limited determinations of the constituents of an object under inspection. Moreover, these conventional scanning probe microscopes cannot define the structure of the object below its surface and cannot define with fine resolution pits, walls, projections, and other structures which prevent the end of the probe tip from coming close enough to the object in these areas for accurate inspection by conventional scanning probe microscopy.
U.S. Pat. No. 5,319,977 describes a scanning probe microscope that utilizes the probe tip to make acoustic microscopy measurements and either atomic force microscopy (AFM) measurements or scanning tunneling microscopy (STM) measurements during the same scanning sequence. The resolution of acoustic microscopy is however rather low in comparison to AFM, STM, or near-field optical microscopy. Moreover, as with conventional scanning probe microscopes, the scanning probe microscope described in U.S. Pat. No. 5,319,977 cannot define those types of structures which prevent the end of the probe tip from coming close enough to the object for accurate inspection.
Furthermore, many objects exhibit areas of varying composition and conductivity. For example, the surface of a semiconductor may change from being conductive to insulative as a function of position. However, no scanning probe microscopes currently exist which are capable of making STM, AFM, near-field optical microscopy, and spectrophotometric measurements during the same scanning sequence in order to properly image and identify such an object.
Moreover, in the past microscope systems for Confocal or scanning Probe Microscopy have been limited in the tools available for manipulating the 2D, 3D and volume image characteristics they generate.
In addition, they have been limited in the ability (particularly in Scanning Probe Microscopy) to make accurate measurements in x,y, and z directions. In particular it is useful to have accurate position feedback when operating a Scanning Probe Microscope in order to close the control loop in positioning and repositioning the Scanning Probe.
Furthermore the collection of sectional data in volume confocal microscopy has taken substantial amounts of time making some measurements of time varying specimens difficult or impossible.
The foregoing problems are solved by a scanning probe microscope assembly that has an AFM mode, an STM mode, a near-field spectrophotometry mode, a near-field optical mode, and a hardness testing mode for examining an object.
The scanning probe microscope assembly includes a probe having a base. The probe also includes a cantilever connected to the base, a tip connected to the cantilever, and a clamp connected to the base.
The scanning probe microscope assembly is configured to induce atomic force interaction between the tip and the object and to detect deflection of the cantilever due to the atomic force interaction during the AFM.
The scanning probe microscope assembly is also configured to induce and detect a tunneling current between the tip and the object during the STM mode. During the STM mode, the cantilever is held rigid with respect to the base.
The scanning probe microscope assembly includes a spectrophotometer which has a light source optically coupled to the tip. The light source is controlled to provide light to the tip during the spectrophotometry mode. The tip is shaped so that it emits the provided light at the sharp end of the tip. The emitted light then optically interacts with the object. The spectrophotometer includes a photodetector for detecting light that results from the emitted light optically interacting with the object in order to make spectrophotometric measurements of the detected light.
The scanning probe microscope assembly is also configured to rotationally polarize the light provided by the light source of the spectrophotometer during the near-field mode. The scanning probe microscope assembly identifies deep surface features based on the light detected by the photodetector that results from the rotationally polarized light being emitted by the tip and optically interacting with the object.
The scanning probe microscope assembly is also configured to direct the tip to penetrate the object at a specific point with a predefined known force. The light source is controlled to provide light to the tip during the hardness testing mode before and while the tip penetrates the object. The photodetector detects the light that results from the emitted light optically interacting with the object before and while the tip penetrates the object. The scanning probe microscope assembly compares the resulting light detected before the tip penetrates the object with the resulting light detected while the tip penetrates the object to determine the hardness of the object.